1. Field of the Invention
The present invention relates to projection display apparatuses such as three-liquid-crystal-display projector apparatuses.
2. Description of the Related Art
In recent years, projection display apparatuses have been commercialized in which white light emitted from a light source is separated into components of three colors of red (R), green (G), and blue (B), which are modulated by corresponding light modulating elements and are subsequently integrated together, whereby an image is projected on a screen.
Examples of such projection display apparatuses include those having a discharge lamp as a light source and those having transmissive liquid crystal display devices or digital micromirror devices (DMDs) as light modulating elements. Various improvements have been made to such devices and optical systems. Particularly, projection display apparatuses including higher-resolution reflective liquid crystal display devices have also been commercialized.
A typical projection display apparatus operates as follows: White light emitted from a light source is separated into components of three colors of R, G, and B by dichroic mirrors. Then, the separated components are modulated by corresponding light modulating elements. Subsequently, the components are integrated together by a cross-dichroic prism or the like. Lastly, the integrated light is enlarged and projected onto a screen by a projection lens.
Referring to FIG. 5, a cross-dichroic prism 70 includes four triangular prisms 71, 72, 73, and 74 each having two surfaces thereof covered with an optical thin film so as to obtain a desired reflection characteristic. The prisms 71 to 74 are bonded together with the film-covered surfaces thereof facing each other, thereby forming a rectangular parallelepiped body.
Japanese Unexamined Patent Application Publication No. 9-90510 discloses a projection display apparatus including liquid crystal display devices in which the occurrence of shade on a screen is suppressed by arranging convex lenses provided in optical means (multi-lens arrays) in a staggered manner.